Subscribers&#39; line testing system



Jan; 22, 1946.

H. E. COREY ET AL SUBSCRIBERS Filed Sept. 15, 1944 LINE TESTING SYSTEMT24 T25 TZC TZD TZE INVENTORS HE C (may 2 1 5 Sheets-Sheet 1 Jan. 22,-1946.

H. E. COREY ET AL SUBSCRIBERS LINE Filed Sept.

2,393,236 TESTING SYSTEM 15', 1944 5 Sheets-Sheet 2 INVENTORS HE Cpl ea? I. WW]; I v

A TTORN Y Jan. 22; 1946. H. E. COREY ETAL LINE TESTING-SYSTEMSUBSCRIBERS s Sheets-She a: 5

Filed Sept. 15, 1944 Q5 mg kbwommwnw 'INVENTORS Coreywfi ZZE E ATTORNEYJan. 22, 1946. H. E. COREY ETAL SUBSCRIBERS LINE TESTING SYSTEM v FiledSept. 15, 1944 5 Sheets-Sheet 4 E We.

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H. E. COREY ET AL SUBSCRIBE-RS LINE TESTING SYSTEM 5 Sheets-Sheet 5Filed Sept. 15, l944 I'M HI ar" INVENTORS EE COIZQ! 1% F 1 W?! A T ORNEPatented Jan. 22, 1946 STATES i I oFFm zesazat v 2,393,231; f hsnnsoe-reizasminn TESTINGSYS'IEM Hbr'ace Edmund Corey, nesv'iiie; ahe-Frank Wright, Trenton; N. 3;, assign'ors to American 7 Telephone andTelegraph company; a corporation of New York Application September 15,1944, sh me. 554,194 18 Claims. (c1. 179''175.l1')

This invention relates to testing systems and more particularly toapparatus for testing subs'c'ribers lines in telephone-systems. Stillmore part-icularly,'this invention relates to apparatus for performingroutine tests on subscribersfline circuits in order to detect incipienttroubles of such'mag-nitude as to adversely affect service; as well'asto detect actual trouble conditions. In central ofiice'sem'plo'yingautomatic 'di'al' control switchin'g apparatus; it is important to makeI periodic testsof the subscribers "line's seas to determine whethersatisfactory service can be given over the'lines. Such tests haveheretofore been'performed by attendants equippedwith'testinga-ppara'tuswhich would be manually switched from onesubscribers line to another. The attend'ants would test each line todetermine whether the line is busy and. then if the line is found idle,they would proceed to measure the J insulation; resistance between eachconductor of the-lineand-ground-as well as the insulation resistancebetween both conductors of the line. Such manual tests naturally consumea great deal of time and are therefore quite-costly.

It is therefore an object of this invention to provide an automatictesting apparatus which may progressively test many subscribers lines ina brief interval of time and at the same time supmy a visual indicationof the number of each line being tested at any moment,

Another object of this invention is to provide such automatic testingapparatus withmeans for determining whether any of the subscribers linesare busy and for passing such lines, while all nonbusy lines will betested by'the apparatus of the invention; l 1

Another object of this invention is to provide the automatic testingapparatus with means which will be responsive to a faulty subscribers iline condition to causethe automatic testing apparatus to cease making.any further routine tests on other subscribers"lines. This willenablethe attendant to make an individual test of the faulty line after itsnumber hasbeen noted and recorded and then to correct desired. v

Another object of the invention is to provide the automatic testingapparatus withmeans for testing the various subscribers lines for anypredetermined insulation resistance merely by openating any one of aplurality of switches each of which corresponds to a different value ofinsulatio'n resistancefor test purposes. It is" anobject of theinvention to set theautomatic testing apparatus to perform the routinetests at any assigne'd'valu'e of insulation resistance withoutrequiringiurther adjustments of the testing app'a-' measured bytheautomatic testing' apparatus the faulty condition if so i enables theattendant to take into account different conditions of weather ortemperature or any other factors that may change from time to time.andvmay therefore influence the tests.

This invention will be better understood from the mere detaileddescription hereinafter followingiwhenl read in connection with theaccompanyingdrawings, in which Figure 1 illustrates certain cf theimportant componentsv of the automatic testiiig apparatus employed fortesting any one of a plurality'of lines, and Figs. 2, 3, a'nd 5 togethercomprise a detailed arrangement which may be embodied in automatictesting apparatus for progressively testing the, various lines. 7

Referring to Fig. lot thedrawingacm of the linesto bete'sted includestwo conductors designated)? and R which; it .may be assumed, has beenpreviously testedan'd found idle and from which the centraloiiicebattery (not shown) has been rernovednfor the time required to performtlielsub sequent tests. The arrangement includes ast'ep-byste'p selectorTS offthe rotary typ ehaying sixj arcs, the first two o'fwhich, markedBRDG, include movable brushes of the bridging type, while the other for, designated NBG, include movable brushes of the non-bridging type; Thecontrol orstepping magnet of the selectorTs is designated'IfSM. A vacuumtube VT which may be ofany wei'i-irnown type, is illustrated to ineludethree electrodes,name1y, a cathode, a controlgrid and anianodep Thecontrol grid is connected'teground through a comparativelyrlargeresistorTZK. 'I'h'ecor'itrolgrid is also connected to" thenegativeltermina'l of the battery 'I'BB, the positive terminal" ofwhichiis' connected in common to the swingers or a'plurality ofswitchesde'signatedTO', Ta, TB, To, TD and TE. The switches TE correspond to andcontrol the cohnettion of the resistorsTZA TZE respectiv'ely, tothejcircuit, The contact of the sw'itch'TOis" wired to terminal No; 2 of arel of the selector iis which, as will be shown later, may be connected toone of'tl'ie conductors, such as T,

-' i or the'line tbbe tested'lr The control grid of the tube v'r is als'o connected through aresistor TZJ to terminal No. 0 of are 3 of selectorTS. resistor is of a comparatively small magnitude and maybe employedmercuric the control grid of the tube'VT as'will be explained. A relayI? is associated with the anode cath'ode electrodes of the tube VTIThis" relay has two windings, the upper of which s included; along withthe usual plate battery, in the circuit of the anode and cathode ofthe'tube VT. The lower winding of the relay I'P isconiie c'ted in serieswith a battery and; supplies biasir'ig current continually to thiswinding of the relay; The magnetic effects of e these twowindings' areiii opposed relation to each other, the lower tending to" release therelay while the upper winding tends to operate the relay or hold itoperated.

The upper armature and the make contact of relay TP are connectedbetween the contact No. 2 of are 5 of the selector TS and the backcontact of the armature of relay T1". The winding of relay TT is Wiredto terminal No. f are 6 of the selector TS and it is normally operatedover a circuit which includes battery, the Winding of relay T1, thefeeder brush and main brush of are 6 of the selector TS and ground atterminal No. 1 of this same arc. The relay TT is of the slow releasetype and acts as a timing device for timing the advance of the selectorTS. By so timing the circuit it is possible to control the magnitudes ofvoltage of battery TBB, for example, which may be applied to theconductors of the line to be tested, as will be explained.

After the line having conductors T and R has been seized, the automaticequipment will act to close a switch such as TSW for starting theroutine tests of the insulation resistance of the line. The magnet TSMwill then become energized over a circuit includingbattery, the windingof the magnet TSM, contact No. 0 of are 5 of the selector TS, the feederand main brushes and contact N0. 1 of this selector, switch TSW andground. As soon as the magnet TSM becomes energized, it attracts itsarmature and thereby opens its back contact, whereupon the selector TSwill move all of the main brushes on its six arcs simultaneouslyto theirrespective contacts No 2. Immediately after the main brush of arc 6 ofthe selector leaves its contact No. l, the windingof relay 'IT willbecome deenergized but the latter relay will become fully released apredetermined interval of time thereafter due to its slow releaseproperty. At the same time the control grid of the tube VT will becomepractically grounded over a circuit completed through resistor TZJ andthe feeder brush and main brush of .arc 3 and its contact No. 2 andground. By so grounding the control grid of the tube VT, a substantialcurrent will traverse the upper winding of relay TP so as to hold therelay operated. Furthermore, the battery TBB will be connected in acircuit which includes the conductor T of the line and the resistor TZK,as will now be'explained, this circuit causing current .to traverseresistor TZK of a magnitude which varies inversely with the insulationresistance of the conductor T. The application of battery TBB to theline will condition the line by bringin the tip conductor T to apredetermined voltage with'respect to the ring condu'ctor R Theresistors TZA, TZB, TZC, TZD and TZE may be equal resistors of, forexample, 50,000 ohms each. By closing switch TA the correspondingresistor TZA will be connected between the positive terminal of batteryTB and conductor T of the line through terminal No. 2 and the main andfeeder brushes of are I of the selector SE. If the switch TB were closedinstead ,of. switch TA, then both resistors TZA and T23 would beinterposed in series with each other in the path between the positiveterminal of battery TB and conductor T of theline. Hence.

by closing any one ,of the switches TA to TE,

it is possible to interpose any desired magnitude which case thepositive terminal of battery TBB will be connected'to the conductor T ofthe line throughthe brushes of are l of the selector.

Thus it is possible to 'interpose any desired amount of resistance intothe circuit which includes conductor T of the line, battery T33 and Calresistor TZK. If the line is to be tested for an insulation resistanceto ground of 300,000 ohms, for example, the switch T0 will be closed toshunt the resistors TZO to TZA out of the circuit and in this case, ifthe insulation resistance to ground exceeds the predetermined value of300,000 ohms assumed in the illustration, a flow of current from thebattery TBB through the previously described circuit which includesresistor TZK will be so small as to render the voltage applied to thegrid of the tube VT at a very small negative potential with respect tothe cathode. This is because the voltage applied to the grid of tube VTis governed by the voltage across resistor TZK and the voltage acrossresistor TZK is governed by the flow of current from battery TBB throughboth resistor TZK and the insulation resistance of conductor T.Consequently, an appreciable current will flow through the upper windingof relay TP when the insulation resistance exceeds the above mentionedpredetermined value and the relay will therefore be held operated. Onthe other. hand, should the insulation resistance to ground be foundlower than the predetermined value of 300,000 ohms, a'greater currentwill flow through the series circuit including battery T33 and resistorTZK, and therefore the negative voltage applied to the control grid ofthe tube VT will be of a higher value. The current now traversing theupper winding of relay TP will be reduced substantially below itsprevious value, and hence relay TP will be released. The release ofrelay TP will act to stop the selector TS as will be explained later.

As already stated hereinabove, when the selector TS is on its contactNo. 2, the grid of tube VT is practically'grounded and current thenbegins to flow from battery TBB to the conductor T of the line to betested for its'insulation resistance. Simultaneously the line conductorR will be grounded through the brushes of are 2 and its terminal No. 2.After suflicient time interval has elapsed, relay TT will release so asto complete the circuit controlling the magnet TSM ofthe selector TS.The energizing circuit for the magnet includes the grounded armature andback contact of relay TT, the upper armature and make contact of relayTP, contact No. 2 and the brushes of are 5 of the selector, the contactsand winding of magnet TSM, battery and ground. When the magnet TSM isagain energized, it will by causing .the selector TS to step to itscontact No. 3. At contact No. 3 the relay TT will again become energizedover a circuit including battery, the winding of the relay TT, thebrushes of arc 8 of the selector TS, contacts Nos. 3 and 1 of this sameare which are connected to each other, and ground. 1

When the selector TS advances from its ter minal No. 2, the groundpreviously applied through resistor TZJ to the control grid of the tubeVT will be removed. When the selector TS is advanced to its terminal No.3, the battery T33 and the resistor TZK will remain connectedtoconductor T of the line over the path provided by the brushes of are lof the selector and its terminals Nos. 3 and 2 which are connected toeach,

other, and switch-TOwhich may be assumed to be closed for thisillustration. Similarly, the: conductor: R of the line will remaingrounded through the brushes of are 2 and its terminals Nos. 3 and 2.While the selector TS remainson its terminal No. 3 current will continueto flow from the battery TBB to conductor T over the series circuitalready outlined. At-the same time the magnet TSM will again beenergized, the magnet. beingconnected to ground at contactNo. 3 ofarc ofthe selector through the brushes of that are. The opening of the contactof magnet .TSM in response to its operation will now advance theselectorTS to its terminal No.- 4. The winding of the slow release relay TT willthere: fore become deenergized, but before-its armature closes its backcontact,the battery TBB and resistor TZK will remain connected to theconductor T of the line to be tested and, moreover, the conductor R ofthe-line will remain grounded.

If the insulation resistance of the conductor T is less than the valuefixed for the test, the relay T? will become released, as alreadyexplained. The release of the relay TP willbreak the circuit extendingthrough: the winding of magnet TSM and thereby prevent the selector TSfrom making any further steps even when relay TT releases. The releaseof relay.- I'P will result in the operation of the alarm ALM fornotifying the attendant that the line being tested is in faultycondition.

Should there be a short circuit between conductors T'andR of the line.to be tested, an appreciable current will alsoflow through resistor TZKover the circuit including ground at the contacts Nos. 2, 3 and 4 ofare2- of the selector TS and the brushes of that arc, the conductors R; andT which are short circuited to each: other, the brushes of are i of theselector and contacts Nos. 4, 3 and 2 which are connected to each other,switch TO, battery TBB, resistor TZK and ground. This current throughresistor TZK will again render the control grid of tube VT at asubstantially negative voltage with respect to its cathode, therebycausing relay TP to release. This-condition will also operate the alarmALM and at the same time stop the selector TS.

Should there be an accidental cross-connection of battery to the tipconductor T'of the lineto be tested, the negative voltage then appliedto the conductor T will be added to the negative voltage of battery TBBto increase the flow .of current through resistor TZK. The circuitnowwill include, in addition to resistor TZK, battery TBB, switch TO, thebrushesof are I of the selector and conductor T, to which batteryhas-been cross-connected. Again the negative voltage applied to the gridof the tubeVT by the fiow of current through resistor TZK Will 'besufficient to release relay TP. Thus, relay TP will be released if,while the selector TS moves between contacts Nos. Band 4, the insulationresistance of the conductor T is below the predetermined. value forwhich the apparatus is set" to make a test, or if there is a shortcircuit betweenthe line conductors T and R, or if a foreign battery has)been cross-connected to the tip conductor T. In'the absence of any suchfaulty conditions, the relay TP will remain operated and will enable theselector TS to advance to its next terminal. It is to be observed" thatthe cross-connected voltage will generally be negative, as alreadynoted, because the central ofiicebattery. usually has itspo'sitive withthe tip conductor- T of the line,- the' magnet TSM will again beenergized: and a circuitc'ompleted from the grounded armature of relayTT and its back contact, the armature and-make contact of relay TP.terminals Nos. 2"and 4 of are 5 of the selector and its brushes; thecontacts and Winding of magnet TSM, battery andground. The energizationof this magnet will advance the selector TS to its next terminal No. 5.Terminal No. 5- of are l is an open terminal and hence the conductor Tof theline will be disconnected from the battery TBB- and resistor TZK.TerminalNo. 5 of arc 2 of thisselector is likewise an open terminal andhence the ring conductor R of the'line will be ungrounded. However, themagnet TSM will become reenergized over 'a circuit: completed throughcontacts Nos. 5 and-- 3 of are 5 of the selector TS which are connectedtoeach other. and to ground. This will advance the-selector toitsterminal No; 6.

At terminal No. 6 of are I of the selector TS, ground' will now. beapplied to the conductor T of'the line through the. brushes of are l ofthe selector. The conductor R" of thelifie Will" now be connected tobattery TBB' and resistor TZK over a circuit which includesresistorTZK,xbattery TBB, switch'TO, the brushes of. are 2" of theselector and its terminal No. 6, and con ductor Rof the'line. Theselector TS will: take the same steps for conductor R. as those alreadydescribed for conductor T and relay TP will: re main operated either ifthe insulation resistance to ground of the conductor R is-g'reaterthanthe predetermined value, Or if there is no foreign voltageapplied'tothe' conductor R. Onthe' other hand; the presence of one ofthese faulty conditionswill cause relay TP to release and therebyinterrupt any further stepping bythe selector TS.

The circuit of Fig.- l-has been described with switch TO closedand'resistors TZA;.TZB TZD and TZE therefore shunted enter the citcuit; Ifthe line conductors T and R are" to be tested--. for a lower insulationresistance as, for example; 250,000 ohms. then switch- TA will-beoperated instead crewman-"r0. This willinc'liide resistor" TZA in serieswith battery: TBB 'and resistor TZK' and hence relay TP will releaseonly if the insulation resistance is below the predetermined value of250,000 ohms. The vacuum tube system andfrelayTP and the remainder of;the testingapparatus will require" no adjust ments for testing linesi atthis lower value: For testing at a 'stil1 lower insulation resistance;of 200,000 ohms, for example; switch TB win obviouslyi be operated; allother switches remaining un'operated; Then resistors TZA and TZB will beconnected" in series with each other in the testing circuit. Similarly,if switch is operated to the exclusion of allother switches;

all resistorsTZA TZ'E'willbe included inthe' series circuit and hencerelay TP will release if the insulation resistance is below a value of,forexample, 50,000 ohms. The circuit arrangement is free of anyadjustments for changesin the values of the testing conditions and thisis one of the features of the invention.

Figs. 2, 3, 4 and 5 together comprise substantially all of the testingequipment of the invention. Fig. 2 shows part of the testing apparatusand it includes plugs CCP1 and- CCPz which may beconnected to two testconnectors such as-TCi and TCz, respectively, which are shown in Fig. 5.Each test connector of Fig. 5 servesto-gain access to any one of ahundred subscriberslines;

for example; The conductors W 1, W2; .We of Fig. 2 are wired to thconductors of Fig. 3 bearing the same designations. Also, the plugs CA,CB and CC of Fig. 2 engage the jacks TA, TB and T of Fig. 4. 1

The'relay KJ of Fig. 3 is normally operated overa circuit which includesbattery, the winding of relay KJ, the back contact and upper armature ofrelay KH and ground. Ground is applied. to the upper and lower solidbank seg-" ments of the selector KSA of Fig. 3 which, togetherwith theselector KSB'of this figure, are utilized to select any one of thevarious subscribers circuits connected to'one'of the test connectorssuch as TC1 of Fig. as will be explained. The ground extends from theleft swinger and normal contact of key KST, over conductor K1. and thenover two parallel paths oneof'which traverses conductor K2 to the uppersolid bank segment of selector KSA and the other pathtraverses conductorK3 to the lower solid bank segment of selector KSA. The 'relay KC willbe operated over a circuit which includes battery. and the winding ofrelay KC, the upper armature and back contact of relay KV, the lower.inner armature and back contact of relay KD, conductor K4 and the normalcontact "and left swinger of key KST which is grounded.

The stepping magnet .KSMA which controls the selector KSA will beenergized over a circuit which includes'battery, the winding of themagnet KSMA, the upper inner armature and back contactol relay KD,conductor K4 and the normal contact and left swinger of key KST which isgrounded. The operation of the stepping magnet KSMA will advance theselector KSA to its terminal No. 1. On terminal No. 1 the lamp KLr willbe illuminated, the circuit controlling the lamp including battery, lamp16.11 and terminal No. 1 associated with the upper bank of selector KSA,the brushes of the upper bank of this selector. then over conductors K2and K1 to the back contact and left swinger of key KST which isgrounded. The operation of'relay KC also causes the energization of thestarting magnet KSMB which controls the selector KSB, the energizingcircuit including ground at the outer upper armature and make contact ofrelay KC, con-' ductor K5, the winding of the stepping magnet KSMBandbattery. The operation of relay C also places a shunt around "thewinding of relay KHH. It will be observed that the lower terminal of thewinding of relay KHH is grounded, while its upper terminal is nowconnected to ground through resistor KZG and the upper inner makecontact and armature of relay KC. 'Iheoperation of relay KC alsopartially completes a path for the operation of relay KV, the upperterminal of the winding of relay KV being connected to the lower makecontact and armature of relay KC, but relay KV will be operatedthereafter upon the operation of relay KH, as will be explained. I i

1 The right swinger and normal contact of key KST complete a so-calledpulsing circuit extending to the tip and ring terminals T1 and R1 of thetest connector TC 0f Fig, 5 to operate the relay PA of the testconnector. The circuit may be traced from battery and the upper windingof relay PA of the test connector TC1 (Fig. 5) to the ring terminal R1and itscorresponding terminal of the plug CCP1 of Fig. 2, the backcontact of the innermost upper armature of the relay CTR, conductor We,the lower-armature and back contact of relay KHH (Fig. 3), themakebefore-break contact of relay KF, the right swinger and normalcontact of key KST, the back contact and armature of relay KG, conductorWe, the second upper armature and back contact of relay CTR (Fig. 2),the tip conductor T1 of plug CCPI and the corresponding terminal of thetest connector TCi (Fig. 5), the lower winding of relay PA and ground;

The operation of relay PA-of the test connector'TCi causes the operationof relay PB of the test connector over an obvious circuit completedthrough the armature and make contact of relay PA. The operation ofrelay PB connects ground through its upper armature to the sleeveterminal S1. The application of ground to the sleeve terminal S1 of thetest connector and the corresponding terminal of the plug CCPi causesthe relay KH to become operated, the completed circuit including batteryand the winding of relay KI-I, conductor W4, the uppermost armature andback contact of relay CTR, the terminal S1 of plug CCPl, and the sleeveterminal S1 of the test connector which is grounded at the upperarmature of relay PB. The operation of relay Kl-I signifiesthat thepulsing circuit has been completed and that the sleeve terminal S1 ofthe test connector has become grounded. The ground on the sleeveterminal S1 of the test connector also makes the test connector appearbus to any ofiice distributor that may seek access thereto. At the sametime the corresponding sleeve terminal S1 of the other test connectorTC2 will have ground applied to it over a circuit which may be tracedfrom the ground at the upper armature and back contact of relay CZZ andthe sleeve terminal S1 of plug CCPz to the corresponding sleeve terminalof the test connector T02.

In response to the operation of relay KH, the relay KV will becomeoperated, the operating circuit including battery, the winding of relayKV, the lower make contact and armature of relay KC, conductor K11 andthe make contact and armature of relay KH, which is grounded. Theoperation of relay KH also prepares a locking path for relay.KD, thelockingpath including the grounded upper outer armature and make contactof relay KH, conductor K12, and the upper outer armature of relay KD. Itwill be observed that the make contact of the upper outer armature ofrelay KD is wired. to the upper terminal of the winding of thisrelay andhence the relay KD will become locked as soon as it becomes operated.The operation of relay KH also causes the rela KJ to be released byopening the circuit to the winding of relay KJ at the back contact ofthe upper armature of relay KH. The release of relay KJ partiallycompletes 'an operating path for relay KHH, the latter path extendingfrom the back contact and upper armature of relay KJ, through resistorsKZH and KZG to the upper terminal of the winding of relay KI-IH. It isto be observed also that the operation of relay KH connects battery.through the lower armature and make contact of this relay over conductorK21 to the feeder brush of are 3 of the selector KSB. This batterypotential applied to the latter feeder brush will be later utilized foroperating the units lamps KUL1, KUL: KUL'o as the selector KSB isstepped progressively from its terminal No. 12 to its terminal No. 21.The operation of relay KH also partially prepares a locking path forrelay KHH through the make contact of the inner upper armature of relayto lock the relay KHH as soon as it becomes operated.

The operation of the relay KV causes the relay KG to be released byopening the circuit .at'the'winding of the latter relay at the hackcontact of the upper armature of relay 'KV. it is to be noted that relayKC is ofithe slow-torelease type and will release only after apredetermined interval of time has elapsed. The operation of relay KValso causes relay KG to become operated over a circuit from ground atthe lower armature of relay KV and its make contact, the winding ofrelay KG and battery. The relay KG, however, has its upper armature andback contact directly in the pulsing circuit which includes conductor*We and conductor 1W5, as already pointed out, this circuit controllingthe test connector Till. The operation of relay KG, therefore, opens thepulsing circuit and .ideenergizes the winding of relay PA of the testconnector T01, causing the rela PA to release. Therelease of relaytPAwill energize the vertical magnet PVM of the test connector 'TCi over acircuit which extends from ground at the .arm ature of relay PA and itsback contact, the lower armature and make contact of relay E3, thenormal contacts of olf-normal switch "PV-ON, the winding of relay PC,the winding of vertical magnet PVM, battery and ground. This will causethe test connector T61 to take one vertical-step.

The release ofthe relay KC willbreak the-operating circuit of thestepping magnet KSMB .at the make contact of the upper outer armature ofrelay KC. "The release of the stepping magnet will cause the selectorKSB to take one step to its terminal No. 1. The release of relay KC alsoremoves the .shunt around the Winding of'relay KHH previouslyestablished at the upper inner armature of relayjKC, as alreadydescribed. The release of relay KC also releases ,re'layTKV by openingthe circuit in series with the winding of relay at the make contact ofthe lower armature of relay 'KC. There'lease of relayKV in turn breaksthe circuit through the winding of relay KG at the make contact ofthelower armature of relay KV, releasing relayKG. Hence the closure ofthe ibackxcontact oi the armature of relay KG will .recloseithe pulsingcircuitpneviously traced wover eonductors'ws and W rte-relay PA at thetest connector'TCr. become operated over a circuit which may 'be tracedfrom ground at the left swinger of key KST and its normal contact,conductor -Kl, con.- ductor 'the lower solid hank segment ofselectorTKSA and its brushes, and its corresponding terminal N0. 1 then .toterminal .No. 11 of are :6 of the selector KSB and its brushes, thewinding of relay KD, battery and ground. .It is noted also that with the.selector KSB on its terminal No. l, the relay .KQN will become operatedover a circuit which includes ,liatltery, the winding of relay .KON, thebrushes of :are 2 of theiselector KSB, the terminalsNos. l .to 20 .ofthe same-ariawhich are connected to leach other-andground. The relay KQNwill remain operated thereafter as the selector KSB is progressivelyadvanced from its terminal No. 1 to its terminal -No. .-20.

While the selector .KSB is at iitszterminal. No. 1, the relay KT willalso be'operated overia circui which includes battery, the winding :ofrelay K1, the :brushes (of are l :of the selector :KSB andsits terminalsNos. l tolowhichare-connected to each other and ground. Relay :KT will,remain gQHET- ated as the selector KSB is progressively stepped Therelay KD will to its terminal No. 10, but relay will become released asterminal No. 11. is reached b the selector; Relay KT, when operated,grounds the flower terminal vof the winding-of relay KE, there.- byprovidinga shunt aroun t e winding ofrelay to prevent i prematureperation, as will be subsequently described. The relay KD will be lockedin its operated position immediately after it has become operatedthelocking path being completed as already describedby the closure of themake contact of i s upper outer armature. The operation of relay 'KDwill also hold vrelay KC released by opening-the circuit to the windingof relay KC at the back contact of its lower inner armature. The circuitto the winding .of relay KC" wasv previously tracedthroueh the -,b.ackcontact of the upper armature of relay Kv. With relay Kcreleased,themagn t KSMA will remain released and hence theselectqrKSB will takeno ther steps. Thus both selectors KSA and K513 willbe on theirterminals .No. 1. In fact, r l

KD can be operated only when both selectors K541 and KSB have reachedthe same terminals, such as No. 1.

Theoperation of relay KD will also break the circuit to the steppingmagnet .KSMA of the selectorKSA, the circuit being broken {at the backcontactlof the upper ,innerarmature of relay KB. .The release ofmagnetKSMA will revent any further stepping by the selector KSA. At the sametime the operation of relay KD will complate a path to the stepp nmagnet of selector KSB, the path includ n a ound at the lower outerarmature and make contact of re ay the upper .outer armature and makecontact of reIayKON, the brushes of are .5 of the selector KSB .andits,ter-minal No. l, the back contact .and armature of'the stell in magnetKSMB and its winding vbattery and ground. The energization of the steppng ma net KSMB will attract its armature and break :the circuit of thisstepping magnet, thereby advancing the selector KSB to its termmal No.2. Inasmuch as terminalsNos. 2 to :10 .on are 5-.of itheselector KSB:are strapped to ether, (the st pp g ma net KSMB will-be successivelyenergized and released, advancin the selector KSB-to its terminal No.11. The testing circuit will :now ibe ready ior rotary stepping by thetest connector 1 ,01.

vAs selector .KSBnow is onzits terminal No. 5-11 as already described,the relay KT-will zthenbecomereleased :by the breakage of the circuit:to its Winding as thelmorable brush of the are ofthe selector KSBreaches its terminal :No. 11. Aiter the necessary release time ofy-relayKT has elapsed andtheamuaturepf this relay has opened its :makecontact to remove the shuntaround .re lay Kllirelay K=E will-thenibecomebperated. iiI he operatingcincuit for relay ,KE includes battery,resistcrKZA-the w nding .ofrelayKE, theupper inner armature and backcontact of re ay :KR, terminal No. 11 of are 6 of the selectorlQSBiandits brushes, the .upper outer :make contact and armature of relayconductor r-Kiz, the upper make contact and armature of rela =KH andround. During'theintervalrbetween therelease of relay and the operation.ofrelayKE, howv sufficient time will-elapse :to enable the :relay PC ofthe testieonneoted 'SEOi :to :become released, the winding :of :relay,RC being connected in series with the vertical stepping magnet 'PVM ofthe test iconneotor, as alreadyinoted. rheirelease of the-relay :PCrof'the :test connector iillGi will'now mnnect-thexrotaity magnet PROT'of.the test connector to the make contact of the lower armature of relayPBthrough the back contact and armature of relay PC ahdflowerljarniatureof relay PB through the lower rnakefcontacts of the off-normal switchPVON "whichifesponds to the operation of the magnetIPVM. The rotarymagnet PROT, and not the vertical'magnet PVM,

will now be controlled by the pulses transmitted to the test connectorT01. I

circuit through the lower armature and make contactofrelay'Ih'ecperation of relay KR will causeirelay'KG'tojbecomeoperated by thecompletion of an obvious circuit at the make contact of the upper outerarmature of ,relay -The operation'of relay KG willnow perform the samepulsing functions forrotaryfsteppingbythe'teSt connector TC as werepreviously performed by this relay for verticalstepping by the testconnector. "The operation of relay KR. will cause r'elay KE to" bereleased b OPeningthejbircuitin series with the winding of relay KE atthe'back contact of'thej upper inner armatureof relayKR. The relay CCKof Figz'2 will'now be operated over a. path which includes" the groundconnected-to terminals Nos/1 to of are '2 of selector KSB and itsassociated brushes, the lower'make contact and armature orrelay KR,conductor W2, the winding of relay CCK, battery and'ground." Thefunction of relay CCK will be described hereinafter. Therelease'ofrelayKE also breaks the circuitto the stepping magnet KSMB atthe make contact of the upper armature of relay KE. The "release ofstepping magnetKSMB will causethe selector KSB toadvance to its terminalNo; 12. 'On 'terminal'No. 12 the units lamp KUL1 will be illuminated,the circuit for whichincludes lamp KULI; terminal N o. 12 of are 3 ofselector'KSB,-together with its--brushes, the lower make contact: andarmature of relay KH; battery-and ground; l The release or relay KE willalso be followed by the release of relay KR by opening-the circuit tothe winding of relay KR. atthe make contactof the lower armature ofrelay "The-release of relay KR'will'be followed by' therelease of'relayKG upon opening the'circuit' ofthe winding of relay KG at the upperouter make contact and armature of relay KR. With relay KG released, thetest' connector TCi willmake no'further steps at this time but will restupon the terminals of the first subscribers line in the first levelcorresponding to stationNo. -11, whichis the first station ofthe hundredto be tested. The illumination of both lamps KL1 and KULi' corresponds'to the stationthat has been seized by thetestingapparatus.

The testing apparatus being connected to'the subscribers lineNo. 11throughthe test con-- nector TC1, a momentary ground is transmitted tooperate the relay CCK of Fig; 2, as already noted. The operation ofrelay CCK initiates the testing functions of the apparatus. Y a Theoperation of relay CCKcauses relay COS to operate 'over an obviouscircuit completed at the make contact of. the upper outer armature ofrelay CCK. The winding of relayCLQ is paralleled-'tothe winding of relayCOS and he'nce relay CLO will likewise be operated'at this time; The

sleeveterminal S ofv the subscribers line will now be connected to therelajy CBY over a cii'mlit which may be traced from battery the windingof relay CBY, thejlowermake contact and armature of relay CCK," theupper cuter armature and make contact of relay CLO," the lower innermostarmature and back contact of relay CTR to the sleeve terminal S or plugCCE and the sub scribers, sleeve terminal S to which the latter isconnected. If the subscriber's line is busy, ground will be appliedtothe subscribers sleeve terminal S which will: therefore'cause relay 0131to become operated. This will cause the testing apparatus to by-pass thebusy subscribers line and thereby" avoid a test of its condition. Thisis an important featureof the arrangement The previousoperation'of relayCCK as already noted opens the back contactofits inner upper armaturewhich therefore opens the circuit previously traced through the lowerinner armature of relay CTRto the sleeve terminal S of the subscribersline. The back contact of the upper armatureof relay CBY is alsoincluded in series in this same circuit and this contact. is opened inresponse to the operation of relay CBY when a busy subscribers line isencountered. The opening of the latter back contact guards against theoperation of relay CSL shouldthe subscribers line become idle followingthe release of the relayCCK and before the by-pass feature just referredto has had time enough to function, The operation of relay CBY inresponse to a busy'subsc' ribers line operates relay by completing anobvious circuit established by the make contactor the lower armature ofrelay CBY. The relay CBYY then becomes locked in its operated condition,the locking path being completed by theupper armature 'andmake contactof relay CBYY and the-back contactand lower armature of relay CCA whichis connected to ground. The operation of relay COS connects ground tothe upper terminal of the winding of relay CCA' through the make contactand lower armature of relay COS, conductor K20, and'the lowerarmatureand makecontact of relay CLO. Ground will therefore 'be presenton both terminals of the winding of relay 'CCA, providing a shuntcircuit to prevent'the' operation of the latter relay; After relay CCKis fullyreleased, it releases both'relays COS and CLO by opening thecircuits to their parallel windings at the make contact of the upperouter armature of relay CCK. The releaseiof relays COS and CLO removesthe shunt about the winding of relay CCA. The release of relay. CCK alsoreleases relay CBY by opening'the circuit at. the make contact of thelower armatureof relay CCK. The release of relay CBY opens the operatingcircuit of relay CBYY at the lower make contact of relay CBY. but relayCBYY' is slow'torelease.

Now relay CCA is prepared tooperatc and it does operate. The operatingcircuit for relay CCA includes battery the lower armature. and makecontact of relay CBY'Y; conductor K21,-th e resistor CZFQ'the backcontact and upper inner armature of relay CLO, the winding of relay CCAand ground, The relay OBYY is sufiiciently slow to release so as toinsure that relay ,CCA becomes operated notwithstanding that thelockingcircuit o'f-relay CBYY iscompleted through the back 'contact 'ofthe lower armature ofrelay CCA; The relay KE of Fig. 3 will now beoperated in response to the operation of relay CCA-over a circuit whichmay be traced-from ground at the lowerjarrn ature of relay CCAanditsmake contact, conductorWi,

the .backcontact and inner upper armature of relay KR, .the iwindingofrelay YKE, resistor and battery. The 1 operation of relay KE starts thecycleof rotary-motion controlledgenerallyby selector KS3. and :therotary magnet PROTiof the testconnector T01, as alreadyldescribedtoadvance the testconnector 'TClz-one rotary step to the nextsubs-crihers line. :If there is .no .ground on the sleeve terminal S. ofthe subscriber's :line previously reached by thetest connectorTC1because the subscribers line is idle, the p'ass-by;featurel causing.the operation of relay .CBY .will not be invoked .at this time and therelay :CCKxwill release after a sufficient interval .of time haselapsed, thereby causing-thetestin apparatus to proceed to test. theparticular subscribers "line reached'by the test connector 'I'C1.

If :the'subscribefls line .i found .idle, the operation of the .relayCGK .willcause the peration ofrelaysCQS and CLO andthe completionof ashunt around thewinding of the relay CCA, .allof whichzhas alreadyibeendescribed. Therelay-CBZY will. not be operated because no ground ispresent on .the sleeve terminal: S of the subscribers line that-has.been seized. As the relay .CCK. subsequently releases, it removescurrent vfrom the windings. of relays CO6 and CH3, .as already noted.The reIay'COS, beingof the slow release type, allows the relay.CSLsuflicien-t time tooperate-when an vidlesubscriberslineis seized,as'will be explained hereinafter. The relay {ISL will then provide asubstitute ground completed through sth-emake contact of its llQWeloutermost armature and through .the lower armature and make contactofrelay CLO'to theupper terminal ofathe .windingof .relay A to hold theWinding of-rela'y CCA shuntedoutof :the circuit. during- .the timerequired. to complete the test of the subscribersline.

In general, it may be stated that the testing. apparatus of thisinventioniis.arranged to. recognize andrespond-to different conditionson the sleeverterminal of a subscri'bersiline seizedby the apparatus. Anidle subscribers line will have battery on itssleeveit-erminal and will;causerelay SL.:=to. 1 operate. That .idle .subscri-bers zlinezwill thenzbe tested by the apparatus :of this inventionainethegnormal .Abusysubscriberf line v will have -.ground on its. sleeve terminal and .will

cause relay CBXzto. operate. The busy subscribers linerwillithensbepassedby. A vacant subscriber s lineawill ordinarily beconnected to. anintercept trunk-which is .made .busyby. grounding its: sleeve.-

A vacant .subsc-ribers :line will also. .causerelay to operate and hencesuch a line .will =.be nassed'by. 'Ifan open sleeve of ;areg'ularconnectar isencountered, there willbe neither .battery, 5110pground, on the, sleeve and neitherrelay QSLJ I r-CBY will operate. The:testing iappae ii lt swin er QfEKBY CKQALaI- d its:.-malce-.contact,-

esis or F; th xbacki .contactz-and upperiinn armatureof relayCLQ, thewinding-of relayGCA and ground. (The operation of relay 06A will cause.the test connector TCi to advance -to the nextsubscriberis' lineterminal.

- Afteran idle subscriber-s line has been-reached; and relay C(IK aha-sbeen released, current will traverse the upper winding of relay CSL. flhis circuit may ibe traced .from ground, through the upper winding .ofrelayCSL, the upper anonatt re and .back contact of relay. CRY, :theback contact and :upper inner armature of relay CGK', the upper outerarmature and make contact of relay GLO, the .lower innermost. armatureand back contact. of relay :CTR- to the sleeve terminal S of pluglzClCPrand 'the sleeve terminal 8 of the subscriber s :line. The presence ofbattery on--tlle sleeve iterminal S of :an :idle subscriber's line willresult in :the operation of 'relay CSL. Therelay CSLwillithenbelocked.in its operated position, the, locking pathincludingbattery, the lower winding. of relay :CSL,zt-he lowerinnern'iostarma'- ture' and make contact .of relay- CSL, the backcontact and upper armature. of relay con and ground. The winding. of thesubscriber's cut-off relay (notshown) will be connected in seriesiwiththe. upper winding'of relay -G-SL and will therefore the operatedsimultaneously :With relay CSL. The operation of the cut-Off.relaywillremovethe central .ofiicei battery .from the subscribers lineSO-thatthelinerhay be testedfree from any effect due tolthisbattery.

The operation of the relays tCSLand places a shunt around-the windingo-fthe relay CCA, :to prevent. .the advance .of' the :test iconnectorTO]. :to the next subscribers :line. The shunt. path is establishedthrough .the' outermost lower make .contactand armature of relayGSL,the. lower armature and make contact of relay CLO; to. the upperterminal of-thewindin'gof relay.CGA,-thelower-terminal of the winding-ofrelay-GOA beingagrounded. ":Ihiswill prevent the operational relaysCfilAas long as relay CLO-re mainsloperated. The operation. ofrelay CSL-willsimultaneously operate relays-CVR and CVRR, the windings of whichareconnected in parallelrelationship and arecontrolledin commonby-thesecond lower armature and make contact. of relay CS1. RelayCVR'Risof theslow operatetype andhence ground .at the make contact of the:secondlower armature of relay- CSL will be momentarily connected to thestepping magnet TSMnfj'the selector'TlVI of Fig, 4. The-circuitextending to the steppingmagnetTSM includes groundat the makecontact ofthe second lowerarmature of relay-(ISL, theupper armature-andback.contact of relay CV'RR, the sleeve-terminal of plug .CB and:ja-ck'IlB, the brushes of-arc 5 ofthe selectorTS, the back contact andarmatureof the stepping magnet TSM and itSiWll'lding, andbattery. Assoon-as the magnet-TSM is energized, its circuit is then brokentoad'varice the brushes of the selector "ITS to their terminal No. Thiswill start the cycle for testingthe sub'scribers line in the manneralready referred to'withrespect toll 'ig. 1.

The relays CLO and cos will be-held oper relays COS and CLOoperated;the-relay CCA remain shunted out. 01" the circuit-as alreadyexplained, and hence the testconnectorTC1 will be unable to advanceduring theqcycle in-zwhich the seized subscribers." line is beingtested.The operation of relay CSL will also beaccompanied by the shuntingof itsupper winding, .the shunt ircuit extending from the lower terminal ofthe upper winding of relay CSL, through. theupper min ature and backcontact of relay CBY, the back contact and upper inner armature of'relayCCK,the upper outer armature and make contact of relay CLO, thelowerinnermost armature and back contact'of relay CTR to thesleeve terminalS, of plug ,CCPI and the corresponding sleeve terminal S of thesubscribers line. This shunt circuit will hold relay CSL under controlof relay CCA, the .relay CSL remaining operated as long.

as relay CCA. remains released. In this regard it is to be noted thatthelower. winding of relay CSL is connected throughits innermost armatureand make contact to the back contact of the up.

per armature of, relay CCA and to ground, .so that the control ofrelayCSL by. relay CCA is governed by .whether;the relay CCA isreleased, The operation of relay CSL also connects ground through its.uppermost armature andmake contact to the sleeve S of plug .CCP and tothe corresponding sleeve terminal S ofthe subscribers line'for holdingthecut-oif relay (not shown) in the subscribers line circuit operated.This/will insure the removal: of the central office battery from theline as well as the removal of ground from the tip and ring terminalsTand R of thesubscribers circuit as is well understood.

The operation of the relay CSL also completed acircuit to the tip andring terminals T and R ring terminal R maybe traced through the backcontact and lowermost armature of relay. CTR,

the make contact and innermost upper armature of relay CSL, the normalmake contacts of key CKTR, the ring terminals of plug CB and jackTB,.the brushes of arc 2 of selector TS to its terminal No; 2 andground. The tip and ring circuits correspond to the like circuits,previously described in connection with Fig. 1.

7 If thesubscribefls line being tested meets the required conditions,the selector TS will be advanced 'toitsterminal No. 9 in the manneralready fully described with-respect to Fig. 1. However, when themovablebrush of are 4 of selector TS reaches its terminal No, 9, thehold ing circuitfor relays CLOj andCOS previously described 'willhappened at terminal No. 9 of this are. 'Upon the. release of relay CLOthe V shunt path around the winding of relay CCA will be opened-fat thelower make contact of relay CLO and; the relay CCA will become operated.The operating circuit for relay CCA may be traced from ground throughthe winding of relay CCA, the upper inner armature and back contact'oirelay CLO, resistor CZF, thelmake contactand. armature of rela CVR andbattery. The'operation of the relay CCA willnow' provide ground throughits lower armature and make contact to actuate the relay KE, theoperating circuit including the latter contacts ofrelay CCA, conductorW1, the inner upper back contact and armature of relay KR, the windingof relay KE, resistor KZA, battery and ground. Relay KE operated causesrelay KR to operate as well as magnet KSMB to be energized to advanceselector KSB to terminal No, l3.v The operation of relay KR causes relayKG to operate as already described. Relay KG opens the pulsing circuitof relay PA of the test connector T01 to release relay PA. This will beaccompanied by the operation of the rotary magnet PROT over a circuitextending through the armature and back contact of relay PA, thearmature and make contact of relay PB, the lower make contacts of switchPVON, the armature and back contact of relay PC, magnet PROT andbattery. The operation of magnet PROT will advance the test connectorTC]. to the next subscribers line vvwhich will be No. 12. This will beaccompanied by the illumination of lamps KL1 and KULz. The operation ofrelay CCA will also break the circuit of the lower winding of relay CSLat the back contact of the upper armature of rela CCA and this willresult in the release of relay CSL. The release of relay CSL will beaccompanied b the release of relays CVR and CVRR by opening the circuitto the windings of both of these relays at the make contact of thesecond lower armature of relay CSL. The release ofrelay CVR will beaccompanied by the release of rela CCA, the circuit previously traced torelay CCA being opened at the make contact of relay CVR. The release ofrelay CSL will open the circuits previously traced through the secondupper armature and the innermost upper armature, respectively, of relayCSL to the tip and ring terminals T and R of the subscribers linealready tested. The release of relay CSL will also remove ground fromthe subscribers sleeve S at the contact of the outermost upper armatureof 'relay CSIZ, thereby releasing the cut-off relay in the subscriber'sline circuit. This circuit having previously been described need not berepeated.

If the subscribers line is found to have an insufficient amount ofinsulation resistance to ground, for example, the relay CAL will then beoperated. The circuit of relay CAL may be traced from battery and themake-before-break contacts of relayrTP (the latter relay being nowreleased due to the faulty condition of the subscriber's line as pointedout in regard to Fig.1), the tip terminals of jack TA and plug CA thewinding of relay CAL, conductor K38, the left normal contacts of keyCKCA, the ring terminals of plug accompanied by the illumination of lampCTBL and the buzzer CBZ so as to provide visual and audible indicationsto the attendant that the subscribers line under test has been founddefective. The attendant may record the number of the subscriber's lineinvolved in difiiculty and then advance the testing apparatus to thenext subscribers line by momentarily operating thekey CKCA. The breakageof the left normal contact of key CKCA will interrupt the-holdingcircuits of relays COS and CLO. The closure of the right make contact ofkey CKCA will operate relay CCA, the operating circuit includingbattery, the right swinger and make contact of key CKCA, resistor CZF,the back contact and upper inner armature of relay CLO, the winding ofrelay CCA and ground. The operation of relay CCA willamass bfifaccompaniedby thestepping oi selectorKSB- ingfofi thisv transformerfurnishes current for-the filament of thertube. The lower-secondarywinding. of transformer TTR is connected. to the anodes oi the tube:TR'IS', the midpointof the: sec-- on'darywinding being grounded. The:rectified; current will flow over a circuit including ground, the; two:halves of? the. lower secondary transformer-winding, the: twospare'paths of the tube TRT,. the: upper secondary winding oi the.transformenTTl-t, the low pass. filter TEL,- the resistor TZ'R. meterTMA,.the upper winding of relay.- TP- and the: anode and cathodeelectrodes of. the tube the: cathode being. grounded. Thelatter tuheisof the: pentode type; The voltage regu later tube TVR- is bridged:across thefilt-er and; assists in: maintaining a substantially constanltunidirectional voltage; Therectifled: current he transmitted through:resistor TZR;

to thesleevezterminal of jack? TA andth'is cllrrent 7 p the. key CRVwill now beoperated. This will.

may be". employed. to operate the manual testing appaaatus'to: be;described? hereinafter. Some. of thefnectifiying current maybetransmittedl through the resistor TZQ to" the back contact and: upperinner" armatime or relay 'IP. This resistor acts as artificial lbadto*receive a substantial partof the? rectified output ofi'thetube TRTwhen ever the relay Tl? has been: releasedi Another resistor supplies:some of the rectified 120-- tential!v to the screen. grid TSC of thetube TVT' and this: resistor maybeadjusted to fix the'nor'-= mal currenttraversi'ngfthe anode and cathode circuit of the tube: TVT whichincludes the upper winding. of the relay TPas shown; The remainder of.the apparatus of Fig. 4 is substantially thesam e as that..shown=. inFig. I and already described It may be? addedvthat the key TCPm'ay beoperated and held operated so thatcurnent may'fiow from; groimd; throughresistor batteryTBB, the: right 'swirige'r and make contact of key POP,resistors TZF; TZE, TZD; T213 and TZA, the left make contact and swingerof key TQP' back to'- ground; This current through resistor will'imposeanegatitre potential upon: the. control 'grid TCO' oi thetuhe'TVT, thereby controlling'tlie operation of relay The key when:operated'will increase the resistance in" series with resistor" TZKtdreduce the negative potential applied: to the c'ontrol grid TUO; The=resistor TzL is connected tothe'hiasing winding or relay By adjustingresistors TZK and it is possible to operate cry-release the rel'ay TFdepending upon whether key T6? or key TNPisoperat'ed or released; The

steps that are taken by the selector TS ofFig. 4

in testing any particular line'need not be further described;

Ifa manuat test of ad'efective subscribers'line isto be per-formed,thekey'CKTRi willbe operated connect. the; tip and ring terminals T andR of the subscribers line to:- the voltmeter testing circuit of this:arrangement; The operation. of relay provides: arpath: through. itsouterm'ost. lefl:- contacts: to" the winding-of relay GHQ: to hold therelay" CLO operated: In this connectionit is to be remembered that. therelay CLO will-release upon the release of key CKTR. after the manualtest has been. completed; and then the testing procedure will move On tothe. next subscribers line. in order to-test the condi' tion of thisline.

Withkey CKTR operateda test is made for insulation resistance on thering side of the subscribers line. A source of rectified. potential ofsubstantial magnitude previously described as coming from. the. resistorTZR through the sleeve terminal. of jack TA. will be connected. to thering terminal R of the subscribers line. This circuit may befurthertraoed through the sleeve terminal of plug,,CA, thenormalcontactsof key CFE, the voltmeter CVM, the normal left'contactsof keyCRV,v the right make contacts of key- CKTR, the innermost. upperarmature and make contact. of relay CSL, the lower outermost armatureand back. contact of relay CTR to the ring terminal R of plugv C0121and. the ring terminal R of the test connector. TCi. which extends. tothe subscribers line. If ground is-present, on. the ring terminal ofthesubscribers line, the

7 voltmeter. CVlVL will be. actuated and the deflection of its needlemay be noted. The deflection will be a. measure of. the insulationresistanc to ground of the conductor R of the subscriber's line.

To test the tip terminal of. the subscribers line,

connect the same rectified testing voltage to the. tip terminal T. of.the subscribers line. The circuit may be traced from resistor TZRthroughthe sleeve terminals of. jack TA and plug cA the normal contacts of keyCFE,,the.voltmete CVM, the. left make contacts. of key CRV, theleftinnermake contacts of key CKTR, the sec'ondupper' armature and. makecontact of relay CSL, the

. second. lower armature and. back contactofre- .tip terminal. oi thesubscriber's line, the voltmeter CVM Will again be deflected. and; its,d'eflection. should also be noted by the, attendant. The meter;deflection is. likewise proportional to the. insulation resistance toground ofthe tip conductor of the subscribers line.

To. determine whether or not there is a short. circuit between the tipandring terminals T and R; of. the line thev key CRV will be releasedand the key .CG operated. The circuit may now be tracedfrom groundthrough the contacts ofkey CG, the normal. right contactsof key CRV';the lefthinner make contacts of key CK'IR the sec.- ond upper, armatureand make contact of relay CSL, the second lower armature .and'backcontact ci'relay CKTR,.to terminal T at plug. CCPI- and the the terminalT of the subscribers line.- Thiscircuitv will ground the tip terminalofthe line. The direct. voltage may be traced-to the ring terminal. Rthrough resistor TZR, the

. sleeve terminals of. jack TA and plug CA; the

normalcontacts ofkeyCFEthewoltmeter CVM, the 11014112121. left contactsof key GRV, the right make contactsr of key" CKTR. the innermost-upperarmature and make contact. ofi relay CSL; the lowermost armature andvback contact of relay CTR, to the ring-terminal R of plug. CCPr and thecorresponding terminali R1 of the-subscribers line: With ground applied:to the: tip ,terminaiof the? line and asource: of rectified; voltage:anda meter." connected: to the ring! terminal: of thei'li'ne",

alarge current will traverse the meter if the tip and ring conductorsare short circuited, but practically no current will traverse the meterif there isgno short circuit' The deflection. of the meter should benoted; The 'key'CGmay then be released at the end of this test. I

If a fault has been indicated by the testing apparatus causing theoperation of relay CAL and the actuation ofthe indicating devices. 'butno deflection is noted on the voltmeter CVM during the manual testsperformed on the tip conductor T and the ring conductor R and for ashort circuit between these conductors, the fault may have disappearedor, on the other hand. the fault may be due to a cross-connection ofbattery to the line conductors. To determine this, the key CFE may beoperated while key CKTR remains operated and the voltmeter CVM will nowbe connected to observe whether battery is cross-connectedto the ringterminal R of the line. The interconnected circuit may be traced toinclude the make contacts of keyCFE, the voltmeter CVMgthe left. normalcontacts of key CRV, the right makeccritacts of key CKTR, the innermostupper arma-v ture and make contacts of relay CSL, the lowermost,armature and back contact of relay CTR. and over the ring terminal R ofkey CCPI to the ring conductor R. of the line.

the voltmeter CVM. the left make contacts of key CRV, the inner leftmake contacts of key CKTR. the second upper armature and make contact ofrelay CSL, the second lower armature and back contact of relay CTR tothe tin terminal T .of-

plug CCPr andthe tip terminal-T of the subscribersline. .Again-anybattery'ontne .tip terminal Tv will deflect the. voltmeter CVM. The.

It will be noted that when key cm was first. 45

keys ,CRV and CFE maythen be released.

operated it disconnected the subscribers line con ductors T and R fromthe automatic testing apparatus at its left and right inner breakcontacts. This action removedthe fault which was holding the relay .TPunoperated and relay TE therefore reoperates. of the relay TP reclosestheoperating path of magnet TSM, thereby permitting selector TS tocomplete its cycle of operation. Thus, the automatic testing apparatusis in proper. condition so that when the release of key CKTR takesplace.- the seizure of the next subscribers line will be accomplished.

After all of the rotary steps at any one level have been completed, theselector KSB will have been advanced to itsterminal No.22 and relay K ONwill therefore be released.v The relay KHH will then becomeoperated overa circuit which in,- cludes battery, the lower armatureand make contactof relay KH, conductor K 21, the brushes of are 3 of selector KSB, theback contact and armature of relay KJ, resistors KZH and KZG, thewindingof relay KHH toground. The operation of relay KHH opens the pulsingcircuit to relay PA of the test connector TCl previously traced overconductors W5 and We and through the lower armature and back contact ofrelay KHH and the armature and back contact of relay KG, as alreadydescribed. This will prevent the re-closure of this pulsing circuit torelay PA even after relay KG The presenceot voltage on the ring terminalR will deflectfthe' voltmeter CVM and its deflection may be noted.

Closure of the upper outer contactsv becomes released. The operation ofrelay KHH causes relay KF to become operated through an obviouscircuitcompleted by the outer make contact of relay KHH. The operationof relay KF also maintains the pulsing circuit open. Due to theprolonged period during which the pulsing circuit is now held open, thetest connector TC]. will become released. Upon the release of relay PBof the test connector TCr, ground will be removed from its terminal 81and this in turn will cause relay KH to be released. The release ofrelay KI-I will open both'the operating and locking paths of relay KHH.The release of relay KH will of theupper outer armature of relay KHH. At

the same time the release of relay KHH will partially close the pulsingcircuit through conductors W5 and W6. Relay KF is sufiiciently slow torelease, however, to insure the complete restoral of test connector TC;before it recloses the pulsing circuit through conductors W5 and We. Therelease of relay KH will also open the lockingpath level of the testconnector TC].-

to relay KD previously completed through the upper make contact of relayKH and hence relay KD will be released. The release of relay KD willpermit relay KC to become operated as already described. The operationof relay KC connects ground through the upper inner armature of thatrelay to the terminal commonto resistors KZH and KZG, thereby placinga'shunt about the winding of relay KHH and preventing the latter relayfrom operating before the selector KSB reaches its terrninal No. 1..'The release of relay KD completes a circuit to the stepping magnetKSMAcf selector KSA, causing the selector KSA to step to its terminalNo. 2. The test apparatus is now prepared to take two vertical stepsupon the closure of the pulsing circuit in response to the re-:

lease of relay KF, so as to reseize the test connector T01. At the sametime the relay KH will beoperated upon the application of ground tosleeve'terminal S1 through conductor W4.

This same sequence will-be followed for each The advance of the selectorKSA to its terminal No. 2 permits one additional pulse to be producedfor vertically stepping the test connector T01 two steps before re-' layKD'operates. to arrest the vertical stepping.

, The advance of selector KSA to terminal No. 3

will likewise advance the test connector TC1 three steps before relayKD. operates to arrest vertical stepping, etc. When testing'on the ninthlevel is completed, the relay KD will be released to energize magnetKSMA so as to advance the selector KSA to its terminal No. 10. Whenterminal No. 10 is reached, relay KKA will become operated over acircuit which includes battery, the winding of relay KKA, terminal No;10 of the lower bank of selector KSA and its brushes, conductor Ks.conductor K1, the left normal contact of key EST and ground. The relayKKA will then be locked in its operated position, the locking circuitincluding the lower armature and make contact of relay KKA, the innerupper make contact and armature of relay KON'and ground. With relay KONstill operated. the release magnet KRLS will now be energized, thecircuit for which includes battery, the winding of release magnet KRLS,theupper make contact and armature of relay KKA, the inner upper makecontact and armature of relay plurality of series-connected resistors, abattery, a control resistor, means for connecting one terminal of thering conductor to ground and one terminal of the tip conductor in serieswith said battery, said control resistor, and said seriesconnectedresistors, a translating device which is actuated when the voltageacross said control resistor exceeds a predetermined value, means forshunting any group of said series-connected resistors out of said seriescircuit, whereby the testing system will determine whether theinsulation resistance to ground of-the tip conductor exceeds apredetermined value.

3. In a testing system, the combination of a line having tip and ringconductors, a plurality of series-connected resistors, a battery, acontrol resistor, means for connecting the ring conductor to ground andthetip conductor in series with said battery, said control resistor, andsaid seriesconnected resistors, a vacuum tube including anode, cathodeand control electrodes, the control electrode of saidvacuum'tube beingconnected to said control resistor, a translating deviceconnectedbetween the anode and cathode electrodes of said tube, said. translatingdevice being actuated whenithe voltage across the control resistorexceeds a predetermined value, and means ,for shunting any number ofsaid seriesconnected resistors out of said series circuit, whereby thetesting system will determine whether the insulation resistance toground of the tip conductor exceeds a predetermined value.

4. In a testing system, the combination of a line having tip and ringconductors, a step-bystep selector, a source of voltage, an adjustableresistorga control resistor, a translating device connected to saidcontrol resistor and actuated when the voltageacross said controlresistor exceeds a predetermined value, said selector being included inseries circuit with said source of voltage, said adjustable resistor andsaid control resistor,, means for stepping said selector so as toconnect the tip conductor to said series circuit and the ringconductorto ground and for operating said translating device when the insulationresistance to ground is less than a predetermined value, and means forstepping said selector so as to connect the ring conductor to saidseries circuit and the tip conductor to ground so as to operate saidtranslating device when the insulation resistance to ground of the ringconductor is less than said latter predetermined value.

5. In a testing system, the combination of a line having tip and ringconductors, a step-bystep selector, an adjustable resistor, a source ofvoltage, a control resistor, means for connecting said adjustableresistor in a series circuit with said selector, said source of voltage,and said control resistor, a translating device connected to saidcontrol resistor and actuated when the voltage across said controlresistor is below a predetermined value, means for stepping saidselector so as to connect the tip conductor to said series circuit andthe ring conductor to ground so that said translating device will beactuated when the insulation resistance to ground of the tip conductoris below a predetermined value, and means for stepping said selector soas to connect the ring conductor to said series circuit and the tipconductor'to ground so that the translating device will be actuated whenthe insulation resistance to ground of the ring conductor is below thelatter predetermined value, said predetermined value being determined bytip and ring conductors, thecombination of a the magnitude of saidadjustable resistorinr cluded in the series circuit.

6. In a testing system, the combinationoi a line having tip and ringconductors, a step-bystep selector, a source of voltage, a control -re-,sistor connected to said selector and said source of voltage, atranslating device connected across,

said control resistor, said translating device being actuated when thevoltage across said control resistor exceeds a predetermined value,means. for stepping said selector so as to simultaneously connect thetip conductor and the ring conductor to said control resistor and sourceof voltageso: as to determine whether the insulation resistance of saidtip conductor is below a predetermined value, and means for steppingsaid selector so-as to reverse the positions of said tip and ringconductors relative to said control resistor and source of voltage so asto determine whether the insula tion resistance-of said ring conductoris below; the latter predetermined value.

'7. In a testing system, the combination of a line having tip and ringconductors, a step-ebystep selector, a control resistor connected tosaid selector, a source of voltage, a vacuum tlrbehaving an anode,cathode and control electrodes, the control electrode of said tube beingconnected to said control resistor, a translating device connected tothe anode and cathode electrodes of said tube, and means forsuccessively stepping said selector so as to separately connect said tipand ring conductors of said line to said control resistor through saidsource of voltage, whereby said translating device may be actuatedtode-- termine whether the insulation resistance of said conductors isbelow a predetermined value.

8. In a testing system, the combination of a, line having tip and ringconductors, a step-bystep selector, a control resistor connected to saidselector, a vacuum tube having an anode, cathode and control electrodes,the control electrode of said tube being connected to said controlresistor, a translating device connected to the anode and cathodeelectrodes of said tube, means for successively stepping said selectorso as to separately connect the tip and ring conductors of said line tosaid control resistor, and means responsive to the operation of saidtranslating device to prevent further operation of said selector.

9. In a testing system, the combination of a line havin tip and ringconductors, a source of voltage, a vacuum tube having an anode, cathodeand control electrodes, a relay having its winding in circuit with theanode and cathode electrodes of said tube, a resistor connected betweensaid control and cathode electrodes of said tube, a step-by-stepselector, and means to progressiveiy step said selector so as toestablish a path including said source of voltage, said resistor and oneof the conductors of said line, said relay being actuated when theinsulation resistance to ground of the conductorin said path is below apredetermined value.

10. In a testing system, the combination of a line having tip and ringconductors, a source of voltage, a vacuum tube having anode, cathode andcontrol electrodes, a relay having its winding in circuit with saidanode and cathode electrodes, a resistor connecting between said controland cathode electrodes, a step-by-step selector, means to step saidselector to establish a series path including said source of voltage,said resistor and the tip conductor of said line, means to step saidselector to establish a series path including said source of voltage,said resistor and the ringcon ductor of said line, said relay beingactuated when the insulation resistance to ground of the conductor ofthe line included in said series path is below a predetermined value,and means for changing the magnitude of the resistance in the seriespath to correspondingly vary said predetermined value.

ll. In a testing system, the combination of a line having tip and ringconductors, a source of voltage, a vacuum tube having anode, cathode andcontrol electrodes, a relay having its Winding in circuit with saidanode and cathode electrodes, a resistor connecting between said controland cathode electrodes, a step-by-step selector, means to step saidselector to establish a path including said source of voltage, saidresistor and the tip conductor of said line, means to step said selectorto establish a path including said source of voltage, said resistor andthe ring conductor of said line, said relay being actuated when theinsulation resistance to ground of conductor of the line included insaid path is below a predetermined value, and means responsive to theactuation of said relay to prevent further stepping by said selector,

12. In an automatic testing system, the combination of a plurality ofsubscribers lines to be tested, each line having tip and ringconductors, a, relay, a selector connected to said relay, meanscontrolled by said selector for connecting the tip conductor of aselected line to said relay and its ring conductor to ground to actuatesaid relay when the insulation resistance to ground of the tip conductoris below a predetermined value, and means controlled by said selectorfor connecting the ring conductor of the selected line to said relay andits tip conductor to ground to actuate said relay when the insulationresistance to ground of the ring conductor is below said predeterminedvalue.

13. In an automatic testin system, the combination of a plurality ofsubscribers lines to be tested, each line having tip and ringconductors, a relay, a selector connected to said relay, meanscontrolled by said selector for connecting the tip conductor of aselected line to said relay and its ring conductor to ground to actuatesaid relay when the insulation resistance to ground of the tip conductoris below a predetermined value, means controlled by said selector forconnecting the ring :conductor of the selected line to said relay andthe tip conductor to ground to actuate said relay when the insulationresistance to ground of the ring conductor is below said predeterminedvalue, and means controlled by said selector for actuating said relaywhen there is a short-circuit between the tip and ring conductors of theselected line.

14. In an automatic testing system, the combination of a plurality ofsubscribers lines to be tested, each line having tip and ringconductors, a relay, a selector connected to said relay, meanscontrolled by said selector for connecting the tip conductor of aselected line to said relay and its Ting conductor to ground to actuatesaid relay when the insulation resistance to ground of the tip conductoris below a predetermined value, means controlled by said selector forconnecting the ring conductor of the selected line to said relay and itstip conductor to ground to actuate said relay when the insulationresistance to ground of the ring conductor is below said predeterminedvalue, and means controlled by said selector and said relay andresponsive to the non-actuation of said relay to select another line andconnect said relay with said other line so that it may be tested, saidrelay being actuated also when there is a short-circuit between the tipand ring conductors of any selected line.

15. In an automatic testing system, the combination of a plurality ofsubscribers lines to be tested, each line having tip and ringconductors, a relay, a selector connected to said relay, meanscontrolled by said selector for connecting the tip conductor of aselected line to said relay and its ring conductor to ground to actuatesaid relay when the insulation resistance to ground of the tip conductoris below a predetermined value, means controlled by said selector forconnecting the ring conductor of the selected line to said relay and itstip conductor to round to actuate said relay when the insulationresistance to ground of the ring conductor is below said predeterminedvalue, and means responsive to the actuation of said relay to preventthe further operation of said selector.

16. In an automatic testing system, the combination of a plurality ofsubscribers lines to be tested, each line having tip and ringconductors, a relay, a selector connected to said relay, meanscontrolled by said selector for connecting the tip conductor of aselected line to said relay and its ring conductor to ground to actuatesaid relay when the insulation resistance to ground of the tip conductoris below a predetermined value, means controlled by said selectorfor'connecting the ring conductor of the selected line to said relay andits tip conductor to ground to actuate said relay when the insulationresistance to ground of the ring conductor is below said predeterminedvalue, means controlled by said selector for actuating said relay whenthere is a short-circuit between the tip and ring conductors of theselected line, and means responsive to the actuation of said relay toprevent further operation of said selector.

17. In a testin system, the combination of a telephone line having tipand ring conductors to be tested, a step-by-step selector, a relayconnected to said selector, means to step said selector so as to connectthe tip conductor of the line to said relay and the ring conductor toground so that said relay will be actuated if the insulation resistancebetween the tip conductor and ground is below a predetermined value,means to step said selector so as to connect the ring conductor to saidrelay and the tip conductor to ground so that said relay will beactuated if the insulation resistance between the ring conductor andground is below said predetermined value, and means responsive to theapplication of a cross-potential to either tip conductor or ringconductor to actuate said relay.

18. In a testing system for a telephone line to determine whethervoltage has been crossconnected to said line, comprising a source ofvoltage connected to said line and poled so as to be additive to anycross-connected voltage on said line, a resistor connected in serieswith said source Of voltage and said line, and a translating deviceconnected across said resistor and actuated when the voltage across saidresistor exceeds a predetermined value.

HORACE EDMUND COREY. FRANK WRIGHT.

